Differential Radiothermal Methods for Satellite Retrieval of Atmospheric Humidity Profile

The existing radiometric methods for measuring the profile of the water-vapor concentration from spacecrafts are analyzed. Questions of the sensitivity of radiometric measurements to a deviation in the water-vapor concentration from the standard profile are considered. It is shown that the traditional measurements near absorption line 183 GHz have a low sensitivity to a change in the water-vapor concentration in the lower troposphere. A new differential method of humidity measurement in the lower troposphere has been proposed based on measurements near the 22-GHz line. The advantages of differential measurements near 22 GHz when compared to similar measurements in the vicinity of 183 GHz are confirmed by the results of computer simulation.